# How Do You Calculate the Final Speeds of Pucks After a Collision?

• atlbraves49
In summary, the conversation is about a collision between two pucks on an air-hockey table. The pucks have different masses and velocities before the collision, and after the collision, they fly apart at different angles. The person asking for help is given a hint to use the conservation law for angular momentum to solve the problem. They eventually figure it out on their own.
atlbraves49
I can NOT figure this question out, it's the only one I haven't gotten, can someone help?

The drawing shows a collision between two pucks on an air-hockey table. Puck A has a mass of 0.020 kg and is moving along the x-axis with a velocity of +5.5 m/s. It makes a collision with puck B, which has a mass of 0.040 kg and is initially at rest. The collision is not head-on. After the collision, the two pucks fly apart with the angles shown in the drawing.

(a) Find the final speed of puck A.
______ m/s
(b) Find the final speed of puck B.
______ m/s

Hi atlbraves,

usually you must propose a solution or give some hints ...but today I'll make an exception for you:

You must write the the conservation law for angular momentum:

$$\vec{p_{A0}}=\vec{p_A}+\vec{p_B}$$

Then you have to write the above vectorial equation on Ox (the direction of the initial velocity of A) and Oy (perpendicular on it):

Ox: $$p_{A0}=p_A \cdot cos(\alpha_A)+p_B \cdot cos(\alpha_B)$$
Oy: $$p_A \cdot sin(\alpha_A)-p_B \cdot sin(\alpha_B)=0$$

clive said:
Hi atlbraves,

usually you must propose a solution or give some hints ...but today I'll make an exception for you:

You must write the the conservation law for angular momentum:

$$\vec{p_{A0}}=\vec{p_A}+\vec{p_B}$$

Then you have to write the above vectorial equation on Ox (the direction of the initial velocity of A) and Oy (perpendicular on it):

Ox: $$p_{A0}=p_A \cdot cos(\alpha_A)+p_B \cdot cos(\alpha_B)$$
Oy: $$p_A \cdot sin(\alpha_A)-p_B \cdot sin(\alpha_B)=0$$

thanks, i figured it out, i actually ended up knowing how to do it, the reason i wasnt getting the answer correct is i messed up a calculation, thanks for the help anyways

## 1. What is momentum?

Momentum is a measure of an object's motion and is defined as the product of its mass and velocity. It is a vector quantity, meaning it has both magnitude and direction.

## 2. How is momentum calculated?

Momentum is calculated by multiplying an object's mass (m) by its velocity (v). The formula for momentum is p = m x v.

## 3. What is the law of conservation of momentum?

The law of conservation of momentum states that in a closed system, the total momentum before a collision or interaction is equal to the total momentum after the collision or interaction. This means that momentum is conserved, or remains constant, in a closed system.

## 4. How does momentum affect an object's motion?

An object with a higher momentum will be harder to stop or change direction compared to an object with a lower momentum. Therefore, momentum plays a crucial role in determining an object's motion.

## 5. Can momentum be transferred between objects?

Yes, momentum can be transferred between objects through collisions or interactions. For example, when two objects collide, their momentums can be transferred to each other depending on their masses and velocities.

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